Vibration damping devices have conventionally been known as a kind of vibration damping connecting components or vibration damping supports interposed between members that compose the vibration transmission system. Their application to engine mounts of motor vehicles, for example, has been studied. This type of vibration damping device comprises: a first mounting member to be attached to one component that configures the vibration transmission system; a second mounting member to be attached to the other component that configures the vibration transmission system; and a main rubber elastic body elastically connecting the first and second mounting members.
Meanwhile, a vibration damping device generally has a structure wherein an outer bracket is installed to the second mounting member for the purpose of improving the assembly workability and corresponding to different attaching structures and the like so as to attach the second mounting member to the connecting object such as auto bodies using said outer brackets.
Also, in some vibration damping devices, a stopper member can be installed in order to restrict the amount of deformation of the main rubber elastic body or to restrict the relative displacement of the connecting object at the time of overweight input. As a stopper member, a bound stopper member that restricts the displacement of the first and second mounting members getting closer to each other in the axial direction or an axis-perpendicular stopper member that restricts the relative displacement of the first and second mounting members in the axis-perpendicular direction is usually adopted.
Now, Japanese Patent No. 3846328 (Patent Document 1) shows a structure provided with a stopper portion and a metal stopper for composing a stopper member on the outer bracket. In other words, a step portion that expands in the axis-perpendicular direction is provided on the outer bracket (cylindrical bracket 112 in NO. 3846328), and the upper side of this step portion is made to be a smaller-diameter stopper portion that is located upward off the position of the second mounting member to face the first mounting member in the axis-perpendicular direction. In addition, the step portion is overlapped with a separate metal stopper that extends a given distance in the peripheral direction with a cross section of C-shape, which is fixed to the step portion and the stopper portion. Then, the bound stopper member is devised by having the top surface of the metal stopper abutted against the connecting object on the side of the first mounting member via a dustproof cover, while an axis-perpendicular stopper member is devised by abutting the inner periphery of the stopper portion against the outer periphery of the first mounting member via the dustproof cover.
However, since such a structure described in Patent Document 1 requires a separate metal stopper to be fixed to the outer bracket by welding and the like later, which increases the number of parts and production processes, a simpler structure with less number of parts has been sought.
Meanwhile, the inventors of the present invention have proposed to devise the bound stopper member by bending the upper end portion of the stopper portion toward the outer periphery to extend out, without providing a metal stopper. However, in an attempt to implement such a structure with an outer bracket formed by press work, one finds it difficult to maintain enough strength due to the thin thickness of the portion extended toward the outer periphery. On the other hand, when one tries to keep enough thickness at the portion extended toward the outer periphery, it was found barely realistic in terms that other portions of the outer bracket get thicker than necessary, resulting in a substantial weight increase.